The present invention relates to an image forming apparatus, such as a printer, a facsimile machine or a copy machine, which is capable of forming a toner image on a recording medium, such as a paper sheet, by the electrophotography technique. More particularly, the invention relates to a fixing device for use with the image forming apparatus.
Generally, the image forming apparatus for forming a toner image on a recording medium by the electrophotography technique includes a photosensitive member to be driven to rotate, an exposure mechanism for forming an electrostatic latent image on the surface of the photosensitive member, a developing mechanism for developing the latent image into a toner image, a transfer mechanism for transferring the toner image onto a recording medium, and a fixing device for fusing and fixing the toner image on the recording medium in a manner that the recording medium having the toner image transferred thereto by the transfer mechanism is moved to pass therethrough.
The fixing device, usually, includes a first rotary member to be heated and a second rotary member pressed against the first rotary member. A recording medium having a toner image thereon is moved to pass through a press nip between the first and second rotary members. When passing through the press nip, the recording medium is compressed by those rotary members and heated, whereby the toner image is fused and permanently fixed onto the recording medium.
In the fixing device thus constructed, if a peripheral speed difference is present between the two rotary members, a toner image on the recording medium passing through the press nip (press contact portion) between the rotary members is blurred and the image is disturbed or disarranged. For this reason, the prior technique does not employ such a drive method as to drive and rotate both the rotary members, and instead, employs such a drive method that one of the rotary members is driven to rotate, while the other is rotated as a follower.
In a case where the rotary member to be heated consists of a roller, a long time is consumed for the initial heating of the roller. In connection with this, there is known a belt fixing device in which an endless belt is used for the rotary member to be heated, whereby the initial heating time is reduced.
FIG. 32 is a diagram showing an example of the belt fixing device (JP-A-9-138600).
The belt fixing device includes an endless heat-resistant belt endless heat-resistant belt 6, rollers 7a and 7b for supporting the belt 6 on the inner side thereof, a roller 8 for heating the belt endless heat-resistant belt 6, and an pressure application roller 9 in contact with the outer peripheral surface of the belt endless heat-resistant belt 6. The pressure application roller 9 is driven by a motor M to rotate in the direction of an arrow xe2x80x9caxe2x80x9d, while the belt 6 follows the pressure application roller 9 in rotation.
A recording medium having a toner image formed thereon is moved in the direction of an arrow xe2x80x9cbxe2x80x9d to pass through a press contact portion N between the belt 6 and the pressure application roller 9. When passing the press contact portion N, the toner image is heated and fused, and permanently fixed on the recording medium.
FIG. 58 is a diagram showing another example of the belt fixing device (JP-A-8-334997).
In the belt fixing device, a fixing belt 1 extends around a fixing roller 2 driven to rotate and a heating roller 3 containg a heater. An pressure application roller 4 is pressed against the fixing roller 2 with the fixing belt 1 being interposed therebetween. A recording medium S having a toner image T formed thereon is moved in the direction of an arrow to pass through a pressure contact portion N therebetween, whereby the toner image T is fused and permanently affixed onto the recording medium S.
The heating roller 3 includes guide rings 3a as restricting portions which come in contact with the side ends 1b of the fixing belt 1 to restrict such a behavior of the fixing belt 1 as to move aside.
To prevent such a phenomenon that toner is transferred from the recording medium onto the surface of the fixing belt 1 (called offset phenomenon), the fixing device includes an oil coating roller 5 for coating the surface of the fixing belt 1 with release oil, such as silicone oil, as release agent.
The conventional belt fixing device shown in FIG. 57 has the following problem. When a recording medium S that relatively easily slips, for example, a synthetic resin sheet, is supplied to the press contact portion N between the pressure application roller 9 to be driven to rotate and the belt 6 which follows the pressure application roller in rotation, a slip will occur between the pressure application roller 9 of the drive side and the recording medium and/or the recording medium and the belt 6 of the follower side because of the presence of the easily slidable recording medium. As a result, a peripheral speed of the belt 6 is different from that of the pressure application roller 9. Further, a stable operation of the fixing device will be lost.
The conventional belt fixing device shown in FIG. 58 has the following problem. When a recording medium S that relatively easily slips is supplied to the press contact portion N between the belt 1 to be driven and the pressure application roller 4 which follows the belt in rotation, and as a result, a slip will occur between the belt 1 of the drive side and the recording medium an/or the recording medium and the pressure application roller 4 of the follower side because of the presence of the easily slidable recording medium. As a result, a peripheral speed of the belt 1 is different from that of the pressure application roller 4. Further, a stable operation of the fixing device will be lost.
Particularly in the belt fixing device shown in FIG. 58, the surface of the belt 1 is coated with release oil. Because of the coating of the release oil, the above slip is more likely to occur. The release oil that has been applied to the surface of the belt 1 gradually moves to the ends Nxe2x80x2 of the press contact portion N to reduce a friction force acting between the a fixing roller 2 and the pressure application roller 4 at the ends Nxe2x80x2. Further the release oil that will move the ends Nxe2x80x2 of the press contact portion N also moves to between the belt 1 and the fixing roller 2, to thereby reduce a friction force between the belt 1 and the fixing roller 2. As a result, there is a fear that the fixing operation of the fixing device will be more instable.
Accordingly, an object of the present invention is to solve the above-mentioned problems of the conventional fixing devices for use with an image forming apparatus and to provide a fixing device which stably operates.
According to the present invention, there is provided a first image forming apparatus having a fixing device constructed such that the fixing device includes an endless belt to be heated and a rotary member to be in pressing contact with the endless belt, wherein one of the endless belt and the rotary member is driven to rotate while the other rotates in a follower fashion, and a recording medium having a toner image formed thereon is moved to pass through a part of a press contact portion in the fixing device, whereby the toner image is fused and fixed on the recording medium,
wherein a high grip portion is provided at a portion of the endless belt which is not pressed by the recording medium but pressed by the rotary member.
The present invention provides a second image forming apparatus having a fixing device constructed such that the fixing device includes an endless belt to be heated and a rotary member to be in pressing contact with the endless belt, wherein one of the endless belt and the rotary member is driven to rotate while the other rotates in a follower fashion, and a recording medium having a toner image formed thereon is moved to pass through a part of a press contact portion in the fixing device, whereby the toner image is fused and fixed on the recording medium, wherein a high grip portion is provided at a portion of the rotary member which is not pressed by the recording medium but pressed by the endless belt.
The invention provides a third image forming apparatus having a fixing device constructed such that the fixing device includes an endless belt to be heated, a rotary member which is in pressing contact with the endless belt and longer than the width of the endless belt, and a backup roller, longer than the width of the endless belt, for supporting the endless belt on the inner side thereof at a press nip between the endless belt and the rotary member, wherein one of the endless belt and the rotary member is driven to rotate while the other rotates in a follower fashion, and a recording medium having a toner image formed thereon is moved to pass through a press contact portion in the fixing device, whereby the toner image is fused and fixed on the recording medium, wherein
a high grip portion is provided at a portion of the rotary member which is not pressed by the recording medium but pressed by the backup roller.
The invention provides a fourth image forming apparatus which corresponds to the third image forming apparatus specified such that a high grip portion, which will act on the backup roller, is provided on the rear side of a portion of the endless belt which is not pressed by the recording medium.
The invention provides a fifth image forming apparatus having a fixing device constructed such that the fixing device includes an endless belt to be heated, a rotary member which is in pressing contact with the endless belt and longer than the width of the endless belt, and a backup roller, longer than the width of the endless belt, for supporting the endless belt on the inner side thereof at a press nip between the endless belt and the rotary member, wherein one of the endless belt and the rotary member is driven to rotate while the other rotates in a follower fashion, and a recording medium having a toner image formed thereon is moved to pass through a press contact portion in the fixing device, whereby the toner image is fused and fixed on the recording medium, wherein
a high grip portion is provided at a portion of the backup roller which is pressed by the rotary member.
The invention provides a sixth image forming apparatus which corresponds to the fifth image forming apparatus specified such that a high grip portion, which will act on the backup roller, is provided on the rear side of a portion of the endless belt which is not pressed by the recording medium.
The invention provides a seventh image forming apparatus having a fixing device constructed such that the fixing device includes an endless belt to be heated, a rotary member which is in pressing contact with the endless belt and longer than the width of the endless belt, and a backup roller, longer than the width of the endless belt, for supporting the endless belt on the inner side thereof at a press nip between the endless belt and the rotary member, wherein one of the endless belt and the rotary member is driven to rotate while the other rotates in a follower fashion, and a recording medium having a toner image formed thereon is moved to pass through a press contact portion in the fixing device, whereby the toner image is fused and fixed on the recording medium, wherein
an oil coating mechanism is provided which applies release oil onto the surface of the endless belt, and an oil barrier is provided on the backup roller at a portion thereof between a contact portion of the backup roller where it is brought into contact with the endless belt and a portion of the backup roller where it is not brought into contact with the endless belt but is pressed by the rotary member.
The invention provides an eighth image forming apparatus which corresponds to the seventh image forming apparatus specified such that an oil barrier is further provided on the rotary member at a portion thereof between a contact portion of the rotary member where it is brought into contact with the endless belt and a portion of the rotary member where it is not brought into contact with the endless belt but is pressed by the backup roller.
The invention provides a ninth image forming apparatus which corresponds to the seventh image forming apparatus specified such that an oil barrier is provided at a portion of the backup roller which faces the side end of the endless belt.
The invention provides a 10th image forming apparatus which corresponds to the seventh image forming apparatus specified such that a high grip portion is provided at a portion of the rotary member which is not brought into contact with the endless belt but pressed by the backup roller.
The invention provides a 11th image forming apparatus which corresponds to the seventh image forming apparatus specified such that a high grip portion is provided at a portion of the backup roller which is not brought into contact with the endless belt but pressed by the rotary member.
The invention provides a 12th image forming apparatus having a fixing device constructed such that the fixing device includes a first rotary member to be heated and a second rotary member to be in pressing contact with the first rotary member, wherein one of the first and second rotary members is driven to rotate while the other rotates in a follower fashion, and a recording medium having a toner image formed thereon is moved to pass through a part of a press contact portion in the fixing device, whereby the toner image is fused and fixed on the recording medium, wherein a high grip portion is provided at a portion of one of the first and second rotary members which is not pressed by the recording medium but pressed by the other rotary members.
The invention provides a 13th image forming apparatus having a fixing device constructed such that the fixing device includes a first rotary member to be heated and a second rotary member to be in pressing contact with the first rotary member, wherein one of the first and second rotary members is driven to rotate while the other rotates in a follower fashion, and a recording medium having a toner image formed thereon is moved to pass through a part of a press contact portion in the fixing device, whereby the toner image is fused and fixed on the recording medium, wherein
an oil coating mechanism for applying release oil onto a contact portion of at least one of the first and second rotary members where the one rotary member is brought into contact with the recording medium, is provided, and an oil barrier is provided at least between a contact portion of the rotary member to be coated with the release oil by the oil coating means and a portion of the rotary member where the rotary member is not in contact with the recording medium but is pressed by the other rotary member.
The invention provides a 14th image forming apparatus which corresponds to the 13th image forming apparatus specified such that an oil barrier is also provided between a contact portion of the other rotary member where the rotary member is brought into contact with the recording medium and a portion of the other rotary member where the other rotary member is not brought into contact with the recording medium but pressed by the one rotary member.
The invention provides a 15th image forming apparatus which corresponds to the 13th image forming apparatus specified such that a high grip portion is provided at a portion of one of the first and second rotary members which is not pressed by the recording medium but pressed by the other rotary member.
The invention provides a 16th image forming apparatus which corresponds to any of the first to 15th image forming apparatus, which is specified such that the image forming apparatus is capable of forming toner images on both sides of the recording medium.
The invention provides a 17th image forming apparatus which corresponds to any of the first to 15th image forming apparatus, which is specified such that the image forming apparatus is capable of forming a full color image by superimposing a plurality of different colors.
The invention provides a first belt fixing device which includes a fixing belt to be heated and a rotary member to be in pressing contact with the fixing belt, wherein one of the fixing belt and the rotary member is driven to rotate while the other rotates in a follower fashion, and a recording medium having a toner image formed thereon is moved to pass through a central part of a press contact portion in the fixing belt and the rotary member, whereby the toner image is fused and fixed on the recording medium, wherein
the fixing belt is formed with a belt base as a mesh-like member of which the meshes each have a length shorter than a length of the press contact portion as measured in the circumferential direction, and a surface belt layer made of high release material, which is applied to at least the surface side of a central portion of the fixing base when viewed in the widthwise direction of the fixing base, wherein the fixing base includes exposing portions which are located on both sides of the fixing belt base.
The invention provides a second belt fixing device which corresponds to the first belt fixing device specified such that an oil coating mechanism for coating the surface of the fixing belt with release oil is provided, and of the threads forming the mesh-like member, those threads extending in the widthwise direction of the fixing belt are each formed with an aggregation of a plural number of very fine threads.
The invention provides a third belt fixing device which corresponds to the second belt fixing device specified such that the high release material has preferably a permeability to the release oil.
The invention provides a fourth belt fixing device which includes a fixing belt to be heated and a rotary member to be in pressing contact with the fixing belt, wherein one of the fixing belt and the rotary member is driven to rotate while the other rotates in a follower fashion, and a recording medium having a toner image formed thereon is moved to pass through a central part of a press contact portion in the fixing belt and the rotary member, whereby the toner image is fused and fixed on the recording medium, wherein
a tape-like, high grip member is wound around each side end of the fixing belt and fastened thereto.
The invention provides a fifth belt fixing device which corresponds to the fourth belt fixing device specified such that a winding start end at which the winding of the tape-like, high grip member starts is not lapped on a winding terminating end at which the winding of the tape-like, high grip member terminates.
The invention provides a sixth belt fixing device which corresponds to the fourth belt fixing device specified such that the winding start end of the high grip member is confronted with the winding terminating end in a state that a gap slanted to the axial direction of the pressure application roller is interposed therebetween.
The invention provides a seventh belt fixing device which includes a fixing belt to be heated and a rotary member to be in pressing contact with the fixing belt, wherein one of the fixing belt and the rotary member is driven to rotate while the other rotates in a follower fashion, and a recording medium having a toner image formed thereon is moved to pass through a central part of a press contact portion in the fixing belt and the rotary member, whereby the toner image is fused and fixed on the recording medium, wherein
high grip members are respectively provided around both side ends of the fixing belt, and each the high grip member is formed with an expandable endless belt having an inside diameter smaller than an outside diameter of each the side end of the fixing belt when the endless belt is in a free state.
The invention provides an eighth belt fixing device which includes a fixing belt to be heated and a rotary member to be in pressing contact with the fixing belt, wherein one of the fixing belt and the rotary member is driven to rotate while the other rotates in a follower fashion, and a recording medium having a toner image formed thereon is moved to pass through a central part of a press contact portion in the fixing belt and the rotary member, whereby the toner image is fused and fixed on the recording medium, wherein
high grip members made of cloth are respectively provided around both side ends of the fixing belt.
The invention provides a ninth belt fixing device which includes a fixing belt which is to be heated and formed with an endless belt base and a surface belt layer layered over the belt base, and a rotary member to be in pressing contact with the fixing belt, wherein one of the fixing belt and the rotary member is driven to rotate while the other rotates in a follower fashion, and a recording medium having a toner image formed thereon is moved to pass through a central part of a press contact portion in the fixing belt and the rotary member, whereby the toner image is fused and fixed on the recording medium,
wherein
high grip members are respectively provided around both side ends of the fixing belt, and an outside diameter of each the high grip member is larger than that of the surface belt layer.
The invention provides a 10th belt fixing device which includes a fixing belt to be heated and a rotary member to be in pressing contact with the fixing belt, wherein one of the fixing belt and the rotary member is driven to rotate while the other rotates in a follower fashion, and a recording medium having a toner image formed thereon is moved to pass through a central part of a press contact portion in the fixing belt and the rotary member, whereby the toner image is fused and fixed on the recording medium, wherein
high grip members are respectively provided around both side ends of the fixing belt, and each side edge of a high grip member is not linear in the circumferential direction.
The invention provides an 11th belt fixing device which includes a fixing belt to be heated and a rotary member to be in pressing contact with the fixing belt, wherein one of the fixing belt and the rotary member is driven to rotate while the other rotates in a follower fashion, and a recording medium having a toner image formed thereon is moved to pass through a central part of a press contact portion in the fixing belt and the rotary member, whereby the toner image is fused and fixed on the recording medium, wherein
high grip members are respectively provided around both side ends of the fixing belt, and an uneven pattern on a surface of a high grip member is slanted with respect to the width direction.
The invention provides a 12th belt fixing device which corresponds to the 11th belt fixing device specified such that the uneven patterns on the surface of the high grip member are axially symmetry with respect to the center line as view in the width direction of the fixing belt.
The invention provides a 13th belt fixing device which includes a fixing belt to be heated, a rotary member to be in pressing contact with the fixing belt, and a restricting member which comes in contact with the side end of the fixing belt to restrict such a behavior of the fixing belt as to move aside, wherein one of the fixing belt and the rotary member is driven to rotate while the other rotates in a follower fashion, and a recording medium having a toner image formed thereon is moved to pass through a central part of a press contact portion in the fixing belt and the rotary member, whereby the toner image is fused and fixed on the recording medium,
wherein
high grip members are respectively fastened around both side ends of the fixing belt, and the high grip member comes in contact with the restricting member.
The invention provides a 14th belt fixing device which corresponds to the 13th belt fixing device specified such that a rigidity of the high grip member in the belt width direction is larger than that in the belt circumferential direction.
The invention provides a 15th belt fixing device which includes a fixing belt to be heated and a rotary member to be in pressing contact with the fixing belt, wherein one of the fixing belt and the rotary member is driven to rotate while the other rotates in a follower fashion, and a recording medium having a toner image formed thereon is moved to pass through a central part of a press contact portion in the fixing belt and the rotary member, whereby the toner image is fused and fixed on the recording medium, wherein
high grip members each having a thermal expansion coefficient substantially equal to that of the fixing belt are respectively fastened around both side ends of the fixing belt.
The invention provides a 16th belt fixing device which includes a fixing belt to be heated and a rotary member to be in pressing contact with the fixing belt, wherein one of the fixing belt and the rotary member is driven to rotate while the other rotates in a follower fashion, and a recording medium having a toner image formed thereon is moved to pass through a central part of a press contact portion in the fixing belt and the rotary member, whereby the toner image is fused and fixed on the recording medium, wherein
high grip members are respectively fastened around both side ends of the fixing belt with a flexible adhesive layer being interposed therebetween.
The invention provides a 17th belt fixing device which includes a fixing belt to be heated, a rotary member to be in pressing contact with the fixing belt, and an oil coating mechanism for applying release oil to a surface of the fixing belt, wherein one of the fixing belt and the rotary member is driven to rotate while the other rotates in a follower fashion, and a recording medium having a toner image formed thereon is moved to pass through a central part of a press contact portion in the fixing belt and the rotary member, whereby the toner image is fused and fixed on the recording medium,
wherein
high grip members are respectively provided around both side ends of the fixing belt, and the high grip member has an oil absorption capability.
The invention provides a belt fixing device which corresponds to the 17th belt fixing device specified such that the high grip member allows the release oil to flow in the belt circumferential direction.
The invention provides a 19th belt fixing device which includes a fixing belt to be heated, a rotary member to be in pressing contact with the fixing belt, and an oil coating mechanism for applying release oil to a surface of the fixing belt, wherein one of the fixing belt and the rotary member is driven to rotate while the other rotates in a follower fashion, and a recording medium having a toner image formed thereon is moved to pass through a central part of a press contact portion in the fixing belt and the rotary member, whereby the toner image is fused and fixed on the recording medium,
wherein
high grip members are respectively provided around both side ends of the fixing belt, and the high grip member is made of a mixture of a high friction material and a material having an oil absorption capability.
The invention provides a 20th belt fixing device which corresponds to any of the 8th to 18th belt fixing devices, which is specified such that the high grip member is an expandable endless belt having an inside diameter smaller than an outside diameter of each side end of the fixing belt when the endless belt is in a free state.
The invention provides a 21st belt fixing device which corresponds to any of the 8th to 18th belt fixing devices, which is specified such that the high grip member is a tape-like member, and wound around and fastened to both side ends of the fixing belt.
The invention provides a 22nd belt fixing device which corresponds to the 21st belt fixing device specified such that a winding start end of the tape-like, high grip member is not lapped on a winding terminating end thereof.
The invention provides a 23rd belt fixing device which corresponds to the 21st belt fixing device specified such that the winding start end of the high grip member is confronted with the winding terminating end in a state that a gap slanted to the axial direction of the pressure application roller is interposed therebetween.
The invention provides a 24th belt fixing device which corresponds to the ninth to 18th belt fixing devices, which is specified such that the high grip member is cloth.
The invention provides a 25th belt fixing device which corresponds to any of the 4th to ninth, and 11th to 19th belt fixing devices, which is specified such that each side edge of the high grip member is not linear in the circumferential direction.
The invention provides a 26th belt fixing device which corresponds to any of the 4th to 8th, and 10th to 19th belt fixing devices, which is specified such that the fixing belt is formed with an endless belt base and a surface belt layer formed on a central portion of a surface of the belt base layer, and an outside diameter of the high grip member is larger than an outside diameter of the surface belt layer.
The invention provides a 27th belt fixing device which corresponds to any of the 4th to 19th belt fixing devices, which is specified such that the side ends of the high grip member are beveled.
The invention provides a 28th belt fixing device which corresponds to the 27th belt fixing device specified such that the beveled face is smoothed.
The invention provides a 29th belt fixing device which corresponds to any of the 4th to 14th, 17th and 18th belt fixing devices, which is specified such that the high grip member is made of a material having a thermal expansion coefficient substantially equal to that of the fixing belt.
The invention provides a 30th belt fixing device which corresponds to any of the 4th to 14th, 17th and 18th belt fixing devices, which is specified such that the high grip member is fastened with a flexible adhesive layer being interposed therebetween.
The invention provides a 31st belt fixing device which corresponds to any of the 21st to 16th belt fixing devices, which is specified such that an oil coating mechanism for coating the surface of the fixing belt with release oil is provided, and the high grip member has an oil absorbing capability.
The invention provides a 32nd belt fixing device which corresponds to the 31st belt fixing device specified such that the high grip member allows the release oil to flow in the belt circumferential direction.
The invention provides a 33rd belt fixing device which corresponds to the 31st belt fixing device specified such that the release oil applied by the oil coating mechanism is applied to only a press contact portion on the fixing belt with the recording medium.
The invention provides a 34th belt fixing device which corresponds to any of the 4th to 16th belt fixing devices, which is specified such that an oil coating mechanism for coating the surface of the fixing belt with release oil is provided, the high grip member is permeable to the release oil, and is fastened to each of both the side ends of the fixing belt with an adhesive layer capable of absorbing the oil.
The invention provides a belt fixing device which corresponds to the 34th belt fixing device specified such that the release oil applied by the oil coating mechanism is applied to only a press contact portion on the fixing belt with the recording medium.
The invention provides a 18th image forming apparatus which corresponds to the 1st to 10th, and 13th to 15th image forming apparatus, and the second belt fixing device, which are specified such that
second belt fixing device specified such that the release oil applied by the oil coating mechanism is applied to only a press contact portion on the fixing belt with the recording medium.
The invention provides a 36th belt fixing device which corresponds to any of the 17th to 19th belt fixing devices, which is specified such that the release oil applied by the oil coating mechanism is applied to only a press contact portion on the fixing belt with the recording medium.
The invention provides a 37th belt fixing device which corresponds to any of the first to 19th belt fixing devices, which is specified such that toner images may be fixed on both sides of the recording medium.
The invention provides a 38th belt fixing device which corresponds to any of the first to 19th belt fixing devices, which is specified such that a full color images formed by superimposing a plurality of different colors may be formed on the recording medium.
[Operations and Effects]
In the first image forming apparatus, a recording medium having a toner image formed thereon is moved to pass through a part of a press contact portion in the fixing device, whereby the toner image is fused and fixed on the recording medium. The fixing device includes an endless belt to be heated and a rotary member to be in pressing contact with the endless belt, wherein one of the endless belt and the rotary member is driven while the other rotates in a follower fashion.
In the belt fixing device, a high grip portion is provided at a portion of the endless belt which is not pressed by the recording medium but pressed by the rotary member. Therefore, when a recording medium, which relatively easily slips, is supplied to the part of the press contact portion between the endless belt and the rotary member, and as a result, when a slip will occur between the endless belt (or the rotary member) of the drive side and the recording medium and/or the recording medium and the rotary member (or the endless belt) of the follower side, the endless belt and the rotary member rotate at substantially equal peripheral speeds since the follower action of the endless belt (or the rotary member) of the follower side for the rotary member (or the endless belt) of the drive side is enhanced through the action of the high grip portion. Therefore, the slip is prevented (at least its occurrence is extremely infrequent). As a result, the fixing operation of the fixing device is stable. Accordingly, the toner image on the recording medium is little blurred, so that the resultant image is little disarranged.
In the second image forming apparatus, a recording medium having a toner image formed thereon is moved to pass through a part of a press contact portion in the fixing device, whereby the toner image is fused and fixed on the recording medium. The fixing device includes an endless belt to be heated and a rotary member to be in pressing contact with the endless belt, wherein one of the endless belt and the rotary member is driven while the other rotates in a follower fashion.
In the second image forming apparatus, a high grip portion is provided at a portion of the endless belt which is not pressed by the recording medium but pressed by the endless belt. Therefore, when a recording medium, which relatively easily slips, is supplied to the part of the press contact portion between the endless belt and the rotary member, and as a result, when a slip will occur between the endless belt (or the rotary member) of the drive side and the recording medium and/or the recording medium and the rotary member (or the endless belt) of the follower side, the endless belt and the rotary member rotate at substantially equal peripheral speeds since the follower action of the endless belt (or the rotary member) of the follower side for the rotary member (or the endless belt) of the drive side is enhanced through the action of the high grip portion. Therefore, the slip is prevented (at least its occurrence is extremely less frequent). As a result, the fixing operation of the fixing device is stable. Accordingly, the toner image on the recording medium is little blurred, so that the resultant image is little disarranged.
In third image forming apparatus, a recording medium having a toner image formed thereon is moved to pass through a press contact portion in the fixing device, whereby the toner image is fused and fixed on the recording medium. The fixing device includes an endless belt to be heated, a rotary member which is in pressing contact with the endless belt and longer than the width of the endless belt, and a backup roller, longer than the width of the endless belt, for supporting the endless belt on the inner side thereof at a press nip between the endless belt and the rotary member, wherein one of the endless belt and the rotary member is driven to rotate while the other rotates in a follower fashion.
In the belt fixing device, a high grip portion is provided at a portion of the rotary member which is not pressed by the recording medium but pressed by the backup roller. Therefore, when a recording medium, which relatively easily slips, is supplied to the press contact portion between the endless belt and the rotary member, and as a result, when a slip will occur between the endless belt (or the rotary member) of the drive side and the recording medium and/or the recording medium and the rotary member (or the endless belt) of the follower side, the endless belt and the rotary member rotate at substantially equal peripheral speeds since the follower action of the endless belt (or the rotary member) of the follower side for the rotary member (or the endless belt) of the drive side is enhanced through the action of the high grip portion.
This will be described in detail hereunder.
When the endless belt is driven, its drive force is transmitted to the rotary member which is pressed against the endless belt, and also is transmitted to the backup roller which follows the endless belt in rotation. Thus, the drive force from the endless belt is transmitted to the rotary member by way of two routes.
When the rotary member is driven, its drive force is transmitted to the endless belt pressed against the rotary member, and is also transmitted to the backup roller through the high grip portion. Also in this case, the drive force derived from the rotary member is transmitted tot he endless belt by way of two routes.
Accordingly, in a case where the rotary member is driven and also in a case where the endless belt is driven, the follower action of the rotary member (or the endless belt) of the follower side for the endless belt (or the rotary member) of the drive side is enhanced through the action of the high grip portion. Therefore, even when the recording medium, which relatively easily slips, is fed to the press contact portion, the endless belt and the rotary member rotate at substantially equal peripheral speeds.
The slip is prevented (at least its occurrence is extremely infrequent). As a result, the fixing operation of the fixing device is stable. Accordingly, the toner image on the recording medium is little blurred, so that the resultant image is little disarranged.
The fourth image forming apparatus corresponds to the third image forming apparatus specified such that a high grip portion, which will act on the backup roller, is provided on the rear side of a portion of the endless belt which is not pressed by the recording medium.
With the operation of the high grip portion, the follower action of the endless belt (or the rotary member) of the follower side for the rotary member (or the endless belt) of the drive side is further enhanced. As a result, the fixing device operates more stably. Accordingly, a chance of the blurring of the toner image on the recording medium is more lessened, and as a result, the resultant image is further improved in its quality.
In the fifth image forming apparatus, a recording medium having a toner image formed thereon is moved to pass through the press contact portion in the fixing device, whereby the toner image is fused and fixed on the recording medium. The fixing device includes an endless belt to be heated, a rotary member which is in pressing contact with the endless belt and longer than the width of the endless belt, and a backup roller, longer than the width of the endless belt, for supporting the endless belt on the inner side thereof at a press nip between the endless belt and the rotary member, wherein one of the endless belt and the rotary member is driven to rotate while the other rotates in a follower fashion.
In the belt fixing device, a high grip portion is provided at a portion of the backup roller which is pressed by the rotary member. Therefore, when a recording medium, which relatively easily slips, is supplied to the press contact portion between the endless belt and the rotary member, and as a result, when a slip will occur between the endless belt (or the rotary member) of the drive side and the recording medium and/or the recording medium and the rotary member (or the endless belt) of the follower side, the endless belt and the rotary member rotate at substantially equal peripheral speeds since the follower action of the endless belt (or the rotary member) of the follower side for the rotary member (or the endless belt) of the drive side is enhanced through the action of the high grip portion.
This will be described again detail hereunder for ease of understanding, while it was discussed in the operation description of the third image forming apparatus.
When the endless belt is driven, its drive force is transmitted to the rotary member which is pressed against the endless belt, and also is transmitted to the backup roller which follows the endless belt in rotation. When the rotary member is driven, its drive force is transmitted to the endless belt pressed against the rotary member, and is also transmitted to the backup roller through the high grip portion. Accordingly, in a case where the rotary member is driven and also in a case where the endless belt is driven, the follower action of the rotary member (or the endless belt) of the follower side for the endless belt (or the rotary member) of the drive side is enhanced through the action of the high grip portion. Therefore, even when the recording medium, which relatively easily slips, is fed to the press contact portion, the endless belt and the rotary member rotate at substantially equal peripheral speeds.
The slip is prevented (at least its occurrence is extremely infrequent). As a result, the fixing operation of the fixing device is stable. Accordingly, the toner image on the recording medium is little blurred, so that the resultant image is little disarranged.
The sixth image forming apparatus corresponds to the fifth image forming apparatus specified such that a high grip portion, which will act on the backup roller, is provided on the rear side of a portion of the endless belt which is not pressed by the recording medium.
Accordingly, the follower action of the rotary member (or the endless belt) of the follower side for the endless belt (or the rotary member) of the drive side is enhanced through the action of the high grip portion in the fifth image forming apparatus. Therefore, the slip is prevented (at least its occurrence is extremely infrequent). As a result, the fixing operation of the fixing device is stable. Accordingly, the toner image on the recording medium is little blurred, so that the resultant image is little disarranged.
In the seventh image forming apparatus, a recording medium having a toner image formed thereon is moved to pass through a press contact portion in the fixing device, whereby the toner image is fused and fixed on the recording medium. The fixing device includes an endless belt to be heated, a rotary member which is in pressing contact with the endless belt and longer than the width of the endless belt, and a backup roller, longer than the width of the endless belt, for supporting the endless belt on the inner side thereof at a press nip between the endless belt and the rotary member, wherein one of the endless belt and the rotary member is driven to rotate while the other rotates in a follower fashion. In the belt fixing device, an offset phenomenon is unlike to to occur since an oil coating mechanism for applying release oil onto the surface of the endless belt.
Further, an oil barrier is provided on the backup roller at a portion thereof between a contact portion (corresponding to each end Nxe2x80x2 of a press contact portion N described in connection with FIG. 58) of the backup roller where it is brought into contact with the endless belt and a portion of the backup roller where it is not brought into contact with the endless belt but is pressed by the rotary member. Therefore, when the release oil having been applied to the surface of the endless belt will flow into the xe2x80x9cportion of the backup roller where it is not brought into contact with the endless belt but is pressed by the rotary memberxe2x80x9d, its flow is blocked by the oil barrier (at least little flow is allowed.).
For this reason, a gripping force is sufficiently secured between the backup roller and the rotary member at the xe2x80x9cportion of the backup roller where it is not brought into contact with the endless belt but is pressed by the rotary memberxe2x80x9d, so that the endless belt and the rotary member turn at substantially the equal peripheral speeds (The reason why the endless belt and the rotary member turn at substantially the equal peripheral speeds when a gripping force is sufficiently secured between the backup roller and the rotary member as stated in the operation description of the third image forming apparatus.).
In the seventh image forming apparatus, when a slip will occur between the rotary member of the drive side (or the endless belt) and the recording medium and/or the recording medium and the endless belt of the follower side (or the rotary member), the slip is prevented (at least its occurrence is extremely infrequent.) although such a construction is employed that the release oil is applied to the endless belt, and as a result, a stable fixing operation of the fixing device is performed. Accordingly, the toner on the recording medium is little blurred, and hence the resultant image is little disarranged.
The eighth image forming apparatus corresponds to the seventh image forming apparatus specified such that an oil barrier is further provided on the rotary member at a portion thereof between a contact portion of the rotary member where it is brought into contact with the endless belt and a portion of the rotary member where it is not brought into contact with the endless belt but is pressed by the backup roller. Therefore, when the release oil having been applied to the endless belt and transferred to the contact portion of the rotary member where it is brought into contact with the endless belt will flow into the xe2x80x9cportion of the rotary member where it is not brought into contact with the endless belt but is pressed by the backup rollerxe2x80x9d, its flow is blocked by the oil barrier (at least little flow of it is allowed.).
Accordingly, a gripping force is more satisfactorily secured between the rotary member and the backup roller in the xe2x80x9cportion of the rotary member where it is not brought into contact with the endless belt but is pressed by the backup rollerxe2x80x9d. As a result, a stable fixing operation of the fixing device is performed. Accordingly, the toner on the recording medium is little blurred, and hence the resultant image is little disarranged.
The ninth image forming apparatus corresponds to the seventh image forming apparatus specified such that an oil barrier is provided at a portion of the backup roller which faces the side end of the endless belt. Therefore, when the release oil having been applied to the surface of the endless belt will flow into between the endless belt and the backup roller, its flow is blocked by the oil barrier at the portion of the backup roller which faces the side end of the endless belt (at least little flow of it is allowed.).
Accordingly, a necessary friction force between the endless belt and the backup roller is secured, and the follower action of the endless belt and the rotary member is also enhanced. And the endless belt and the rotary member turn at substantially equal periphery speeds. (The reason why the endless belt and the backup roller turn at substantially the equal peripheral speeds when a gripping force is sufficiently secured between endless belt and the backup roller is as stated in the operation description of the third and fourth embodiments.).
Thus, in the ninth image forming apparatus, a more stable fixing operation of the fixing device is performed although the endless belt is coated with the release oil.
The 10th image forming apparatus corresponds to the seventh image forming apparatus specified such that a high grip portion is provided at a portion of the rotary member which is not brought into contact with the endless belt but pressed by the backup roller. With provision of the high grip portion, the follower action of the rotary member and the backup roller is further improved, and hence the follower action of the endless belt and the rotary member is also so done. This leads to a more stable fixing operation of the fixing device.
The 11th image forming apparatus corresponds to the seventh image forming apparatus specified such that a high grip portion is provided at a portion of the backup roller which is not brought into contact with the endless belt but pressed by the rotary member. Therefore, the follower action of the rotary member and the backup roller is further improved, and hence the follower action of the endless belt and the rotary member is also so done. This leads to a more stable fixing operation of the fixing device.
In the 12th image forming apparatus, a recording medium having a toner image formed thereon is moved to pass through a part of a press contact portion in the fixing device, whereby the toner image is fused and fixed on the recording medium. The fixing device includes a first rotary member to be heated and a second rotary member to be in pressing contact with the first rotary member, wherein one of the first and second rotary members is driven to rotate while the other rotates in a follower fashion.
In the belt fixing device, a high grip portion is provided at a portion of one of the first and second rotary members which is not pressed by the recording medium but pressed by the other rotary members. Therefore, when a recording medium, which relatively easily slips, is supplied to the part of the press contact portion between the two rotary members, and as a result, when a slip will occur between the heating roller as the rotary member of the drive side and the recording medium and/or the recording medium and the rotary member of the follower side, both the rotary members rotate at substantially equal peripheral speeds since the follower action of the rotary member of the follower side for the rotary member of the drive side is enhanced through the operation of the high grip portion. The slip is prevented (at least its occurrence is extremely infrequent). As a result, the fixing operation of the fixing device is stable. Accordingly, the toner image on the recording medium is little blurred, so that the resultant image is little disarranged.
In the 13th image forming apparatus, a recording medium having a toner image formed thereon is moved to pass through a part of a press contact portion in the fixing device, whereby the toner image is fused and fixed on the recording medium. The fixing device includes a first rotary member to be heated and a second rotary member to be in pressing contact with the first rotary member, wherein one of the first and second rotary members is driven to rotate while the other rotates in a follower fashion.
In the belt fixing device, an oil coating mechanism for applying release oil onto a contact portion of at least one of the first and second rotary members where the one rotary member is brought into contact with the recording medium, is provided. Therefore, an offset phenomenon is unlikely to occur.
Further, an oil barrier is provided at least between a contact portion of the rotary member to be coated with the release oil by the oil coating means and a portion of the rotary member where the rotary member is not in contact with the recording medium but is pressed by the other rotary member. The presence of the oil barrier prevents such a situation that the release oil having been applied to the heating roller 1101 flows from its contact portion with the recording medium to the xe2x80x9cportion of the rotary member where the rotary member is not in contact with the recording medium but is pressed by the other rotary memberxe2x80x9d (at least its occurrence is extremely infrequent.).
For this reason, a gripping force is satisfactorily secured between both the rotary members at the xe2x80x9cportion of the rotary member where the rotary member is not in contact with the recording medium but is pressed by the other rotary memberxe2x80x9d.
Accordingly, both the rotary members rotate at substantially equal peripheral speeds although such a construction is employed that the release oil is applied to the contact portion of one of the rotary members where it is brought into contact with the recording medium. Therefore, when a slip will occur between the rotary member of the drive side and the recording medium and/or the recording medium and the rotary member of the follower side, the slip is prevented (at least its occurrence is extremely in frequent). As a result, the fixing operation of the fixing device is stable. Accordingly, the toner image on the recording medium is little blurred, so that the resultant image is little disarranged.
To be more specific, in a case where no measure is taken in the construction where the release oil is applied to the contact portion of at least one of both the rotary members with the recording medium, the release oil that has been applied to the rotary member moves from its contact portion with the recording medium to the xe2x80x9cportion of the rotary member where the rotary member is not in contact with the recording medium but is pressed by the other rotary memberxe2x80x9d, and a gripping force at the portion between both the rotary members is remarkably reduced. A slip will occur between the rotary member of the drive side and the recording medium and/or the recording medium and the rotary member of the follower side. A stable fixing operation of the fixing device will be lost. On the other hand, in the 13th image forming apparatus, presence of the oil barrier prevents such a situation that the release oil that has been applied to the rotary member moves from its contact portion with the recording medium to the xe2x80x9cportion of the rotary member where the rotary member is not in contact with the recording medium but is pressed by the other rotary memberxe2x80x9d (at least a probability of occurrence of the situation is considerably reduced.). A gripping force is satisfactorily secured at the xe2x80x9cportion of the rotary member where the rotary member is not in contact with the recording medium but is pressed by the other rotary memberxe2x80x9d. Therefore, the slip is prevented (at least its occurrence is extremely infrequent.) although such a construction is employed that the release oil is applied to the contact portion of one of the rotary members where it is brought into contact with the recording medium. As a result, a stable fixing operation of the fixing device is secured. Accordingly, the toner image on the recording medium is little blurred, so that the resultant image is little disarranged.
The 14th image forming apparatus corresponds to the 13th image forming apparatus specified such that an oil barrier is also provided between a contact portion of the other rotary member where the rotary member is brought into contact with the recording medium and a portion of the other rotary member where the other rotary member is not brought into contact with the recording medium but pressed by the one rotary member. The presence of the oil barrier prevents such a situation that the release oil, which was applied to the contact portion of the rotary member where it is brought into contact with the recording medium and moved to the contact portion of the other rotary member where it is brought into contact with the recording medium, moves to the xe2x80x9cportion of the other rotary member where the other rotary member is not brought into contact with the recording medium but pressed by the one rotary memberxe2x80x9d (at least a probability of occurrence of such a situation is considerably reduced.).
Accordingly, a gripping force is satisfactorily secured at the xe2x80x9cportion of the other rotary member where the other rotary member is not brought into contact with the recording medium but pressed by the one rotary memberxe2x80x9d. Therefore, a stable fixing operation of the fixing device is secured. Accordingly, there is less chance that the toner image on the recording medium is blurred, so that the resultant image is little disarranged.
The 15th image forming apparatus corresponds to the 13th image forming apparatus specified such that a high grip portion is provided at a portion of one of the first and second rotary members which is not pressed by the recording medium but pressed by the other rotary member. With presence of the high grip portion, a gripping force is more satisfactorily secured at the xe2x80x9cportion of one of the first and second rotary members which is not pressed by the recording medium but pressed by the other rotary memberxe2x80x9d. As a result, a stable fixing operation of the fixing device is secured. Accordingly, there is less chance that the toner image on the recording medium is blurred, so that the resultant image is little disarranged.
The 16th image forming apparatus corresponds to any of the first to 15th image forming apparatuses, which is specified such that the image forming apparatus is capable of forming toner images on both sides of the recording medium. Therefore, there is a case that a recording medium having toner images formed on both sides thereof passes through the part of the press contact portion in the fixing device.
Sometimes the toner on the recording medium reduces the friction coefficient between the recording medium and the rotary member. And it interrupts the oil absorbing by the recording medium. Therefore, in a case where the toner images are formed on both sides of the recording medium, the recording medium is more likely to slip when comparing with a case where the toner image is formed on one side of the recording medium.
In this connection, in the 16th image forming apparatus, the oil barrier is provided between the contact portion of one of the belt and the rotary member which is not pressed by the recording medium but pressed by the other rotary member (or belt), or it is provided between the portion of the belt (or the rotary member) which is coated with the release oil by the oil coating mechanism, which the portion is brought into contact with the recording medium, and the contact portion which is not brought into contact with the recording medium but is pressed by the other rotary member (or the belt). Therefore, even when the toner images are formed on both sides of the recording medium, the slip does not occur (at least its occurrence is extremely infrequent). As a result, a stable fixing operation of the fixing device is secured.
Thus, the 16th image forming apparatus is capable of forming images suffering from no (at least little) image disarrangement on both sides of the recording medium.
The 17th image forming apparatus corresponds to any of the first to 15th image forming apparatuses, which is specified such that the image forming apparatus is capable of forming a full color image by superimposing a plurality of different colors. Therefore, there is a case that a recording medium having a full color image formed on at least one side thereof passes through the part of the press contact portion in the fixing device.
As described above, sometimes the toner on the recording medium reduces the friction coefficient between the recording medium and the rotary member, and it interrupts the oil absorbing by the recording medium. Therefore, in a case where the full color image by superimposing a plurality of different colors is formed on the recording medium, the recording medium is more likely to slip when comparing with a case where the toner image of monochromatic color is formed on the recording medium.
In this connection, in the 17th image forming apparatus, the oil barrier is provided between the contact portion of one of the belt and the rotary member which is not pressed by the recording medium but pressed by the other rotary member (or belt), or it is provided between the portion of the belt (or the rotary member) which is coated with the release oil by the oil coating mechanism, which the portion is brought into contact with the recording medium, and the contact portion which is not brought into contact with the recording medium but is pressed by the other rotary member (or the belt). Therefore, even when the full color image by superimposing a plurality of different colors is formed on the recording medium, the slip does not occur (at least its occurrence is extremely infrequent). As a result, a stable fixing operation of the fixing device is secured.
Thus, the 17th image forming apparatus is capable of forming images suffering from no (at least little) image disarrangement. When combined with the 16th image forming apparatus, it is capable of forming images suffering from no (at least little) image disarrangement on both sides of the recording medium.
In the first belt fixing device of the invention, a recording medium having a toner image formed thereon is moved to pass through a central part of a press contact portion in the fixing device, whereby the toner image is fused and fixed on the recording medium. The first belt fixing device includes a fixing belt to be heated and a rotary member to be in pressing contact with the fixing belt, wherein one of the fixing belt and the rotary member is driven to rotate while the other rotates in a follower fashion.
The fixing belt is formed with a belt base as a mesh-like member of which the meshes each have a length shorter than a length of the press contact portion as measured in the circumferential direction, and a surface belt layer made of high release material, which is applied to at least the surface side of a central portion of the fixing base when viewed in the widthwise direction of the fixing base, wherein the fixing base includes exposing portions which are located on both sides of the fixing belt base. Therefore, the surface belt layer forms a fixing surface for the toner image and the exposing portions form high grip portions, which act on the rotary member.
Accordingly, when a recording medium, which relatively easily slips, is supplied to the central part of the press contact portion between the fixing belt and the rotary member, and as a result, when a slip will occur between the fixing belt (rotary member) of the drive side and the recording medium and/or the recording medium and the rotary member (fixing belt) of the follower side, the fixing belt and the rotary member rotate at substantially equal peripheral speeds since the follower action of the rotary member (fixing belt) of the follower side for the fixing belt (rotary member) of the drive side is enhanced through the action of the high grip portions. Therefore, the slip is prevented (at least its occurrence is extremely less frequent). As a result, the fixing operation of the fixing device is stable. Accordingly, the toner image on the recording medium is little blurred, so that the resultant image is little disarranged.
Further, the high grip portion is formed by merely forming the exposing portions at both ends of the belt base itself. Therefore, the high grip portion of the belt fixing device is superior in strength to a high grip portion additionally provided on the belt base. In this respect, a reliability of the fixing device is improved. Further, the high grip portion of the belt fixing device may be manufactured more easily manufactured than a high grip portion additionally provided or formed on the belt base.
The second belt fixing device corresponds to the first belt fixing device specified such that an oil coating mechanism for coating the surface of the fixing belt with release oil is provided. Therefore, an offset phenomenon will infrequently occur.
As already stated, where the surface of the fixing belt is coated with the release oil, the oil will gradually move to the ends of the press contact portion between the fixing belt and the rotary member. In this connection, in the second fixing device, the fixing base is exposed at both ends of the press contact portion, and the belt base is made of cloth or a mesh-like member of which the threads extending in the widthwise direction are formed with threads each consisting of an aggregation of a plural number of very fine threads. The oil having reached each end of the press contact portion penetrates into the threads each consisting of an aggregation of a plural number of very fine threads of the cloth or the mesh-like member.
Accordingly, a little amount of the release oil is present on the surface of both ends of the belt base. As a result, a gripping force is satisfactorily secured at the both ends of the press contact portion. The slip is prevented (at least its occurrence is extremely infrequent.). A stable fixing operation of the fixing device is performed.
Thus, the second belt fixing device stably operates for fixing the toner image although it employs such a construction that the surface of the fixing belt is coated with the release oil.
The third belt fixing device corresponds to the second belt fixing device specified such that the high release material has preferably a permeability to the release oil. Because of this nature, the oil having being applied to the surface of the surface belt layer penetrates into the surface belt layer, and then to the threads each consisting of an aggregation of a plural number of very fine threads in the cloth or the mesh-like member, and retained in the cloth or the mesh-like member. The retained oil oozes, by its pressure, out of the cloth or the threads at the press contact portion, and further reaches the surface, or the fixing surface, of the surface belt layer to form an oil thin film on the fixing surface. As a result, the oil film is uniformized on the fixing surface, so that a quality of a toner image fixed thereon is improved.
The release oil having permeated into the ends of the belt base moves back to the central portion of the belt base through the cloth or the mesh-like member which forms the belt base. This reduces consumption of the release oil.
Accordingly, in a case where the fixing operation is not performed for a certain time, and the surplus oil will stay at a region near the press contact portion, the oil permeates into the surface belt layer, and to the threads each of an aggregation of a plural number of very fine threads in the cloth or the mesh-like member of the belt base, and is retained in the cloth or the mesh-like member. And a part of the retained release oil flows back to the central portion of the surface belt layer. Therefore, when the fixing operation is not performed for a certain time and then it is operated again, there is less chance that a first recording medium will be soiled by the surplus oil.
In the 4th belt fixing device,
(i) a recording medium having a toner image formed thereon is moved to pass through a central part of a press contact portion between the fixing belt and the rotary member in a belt roller arrangement in which the fixing belt is heated and the rotary member is pressed against the fixing belt, and one of the fixing belt and the rotary member is driven to rotate while the other follows the one in rotation. As a result, the toner image is fused and permanently fixed on the recording medium.
The high grip tape is wound around each side end of the fixing belt and fastened thereto. As a result, high grip portions which act on the rotary member, are formed at both side ends of the fixing belt.
Therefore, when a recording medium, which relatively easily slips, is supplied to the central part of the press contact portion between the fixing belt and the rotary member, and as a result, when a slip will occur between the a fixing belt (rotary member) of the drive side and the recording medium and/or the recording medium and the rotary member (fixing belt) of the follower side, the fixing belt and the rotary member rotate at substantially equal peripheral speeds since the follower action of the rotary member (fixing belt) of the follower side for the fixing belt (rotary member) of the drive side is enhanced through the operation of the high grip portions. Therefore, the slip is prevented (at least its occurrence is extremely infrequent). As a result, the fixing operation of the fixing device is stable. Accordingly, the toner image on the recording medium S is little blurred, so that the resultant image is little disarranged.
(ii) Further, the high grip portions may be formed in such a simple manner that the high grip tapes are wound around both the side ends of the fixing belt and are fastened to the side ends. Therefore, the manufacturing of the fixing belt is simpler than in the case where ring-like, high grip members are fit to both side ends of the belt or where the side ends themselves of the belt are worked to be high grip portions.
In the fifth belt fixing device based on the fourth fixing device, the winding start end 11 of the high grip tape is not lapped on the winding terminating end. Therefore, the following advantageous effects are produced.
If the winding start end 11 of the high grip tape is lapped on the winding terminating end, the lapping portion 31 is thick. Therefore, a speed of the turning fixing belt when the lapping portion is pressed on the rotary member will be different from that when the lapping portion is not pressed on the rotary member.
When the lapping portion is pressed against the rotary member, stress will concentrate at a portion of the rotary member where it is in contact with the lapping portion. As a result, an endurance of the rotary member will be reduced.
In this connection, in the 5th belt fixing device, the winding start end of the high grip portion is not lapped on the winding terminating end. Because of this, the speed of the turning belt fixing belt little varies. Additionally, little stress concentrates on the specific location of the rotary member, so that the endurance of the rotary member is little reduced.
In the sixth belt fixing device based on the fifth belt fixing device, the winding start end of the high grip member is confronted with the winding terminating end in a state that a gap slanted to the axial direction of the rotary member is interposed therebetween. Therefore, the follow advantageous effects are produced.
If the winding start end and the winding terminating end of the high grip member are not slanted (with respect to, for example, the axial direction of the rotary member), a traveling speed of the fixing belt when the gap between the winding start end and the winding terminating end is in contact with the rotary member will be different from that when it is not in contact with the rotary member. On the other hand, a probability of creating the above-mentioned speed difference of the fixing belt (or the rotary member) of the follower side is small in sixth belt fixing device since the winding start end of the high grip member is confronted with the winding terminating end in a state that the gap slanted to the axial direction of the rotary member is interposed therebetween.
The seventh fixing belt has the advantageous effects (i) of the 4th fixing device, and further the following advantageous effects.
In the 7th belt fixing device, the high grip portion is formed with an expandable endless belt having an inside diameter smaller than an outside diameter of each side end of the fixing belt when it is in a free state. Therefore, by the utilization of its expandability, the belt-like high grip member is expanded and fit to the side ends of the fixing belt to form a high grip portion well fit to and around the side ends of the fixing belt.
Where the high grip tape is wound around each side end of the fixing belt, there is a fear that high grip tape is easy to peel off the belt at its seam. In the fixing belt in this fixing device, such a fear is not present and the belt-like high grip member doubles as a reinforcing member for the side end of the fixing belt. In this respect, a reliability of the fixing belt is improved. As a result, the fixing belt may be thinned in structure. The fixing belt well follows an unevenness corresponding to the amounts of attached toner forming a toner image. This results in improvement of a fixing strength or a fixing uniformity. Further, a heat capacity of the fixing belt is small, so that it may be heated quickly.
The eighth fixing belt has the advantageous effects (i) of the fourth fixing device, and further the following advantageous effects.
Since the high grip portion is formed with the cloth a surface of the high grip portion is defined by a number of vertical and horizontal fine ridges of the threads (woven or knitted) running crosswise and lengthwise. The fine ridge crossing pattern spreads substantially uniformly over the surface.
A vibration and a speed variation, which are generated at both ends of the fixing belt by a drive force transmission, are extremely reduced, thereby ensuring a smooth drive force transmission.
Since the fine ridge crossing pattern are formed by the threads, each ridge is rounded in cross section. With this configuration of the ridges, the stress concentration is lessened, and hence the endurance of the rotary member will be increased.
Further, the high grip portion of this fixing device is superior to that formed with a rubber member of an uneven surface in the strength (particularly to shearing).
Accordingly, in the case of the high grip portion made of a film or a rubber member, for example, when a shearing force is applied to its edge, the edge first cracks, and then the crack rapidly propagates and the high grip portion is finally broken. In the case of the high grip portion made of the cloth, when the fiber at the edge of the cloth cracks to be broken, the breakage of the fiber does not propagates. That is, only one fiber at the edge is broken.
When the side edge of the belt is brought into contact with the inner surface of a flange (the guide ring) of the roller on which the fixing belt is put in order to restrict a zig-zag traveling of the fixing belt, a shearing force acting on the side edge of the belt is great in magnitude. In this fixing device, the high grip portions of cloth are provided on both side ends of the fixing belt. Therefore, the high grip portion is reluctant to its breakage and propagation of the breakage to the whole fixing belt 110 is also greatly impeded.
The high grip portions may be formed by merely fastening them on both side ends of the fixing belt. Therefore, the manufacturing of the fixing belt is simpler than in the case where the side ends themselves of the belt are worked to be high grip portions.
The ninth fixing belt has the advantageous effects (i) of the 4th fixing device, and further the following advantageous effects.
The outside diameter of the high grip member is larger than that of the surface belt layer. Therefore, at both the ends of the press contact portion between the fixing belt and the rotary member, the high grip members are pressed against the rotary member by a larger pressing force. Accordingly, a gripping force is satisfactorily secured between the fixing belt and the rotary member. And the slip is prevented with certainty (at least its occurrence is extremely infrequent.). As a result, a stable fixing operation of the fixing device is secured.
The 10th fixing belt has the advantageous effects (i) of the 4th fixing device, and further the following advantageous effects.
In this fixing device, each side edge of the high grip member is not linear in the circumferential direction, and therefore the following advantageous effects are produced.
If each side edge of the high grip member is linear in the circumferential direction, positions of the rotary member, which is to be in pressing contact with the fixing belt, at which it is pressed against the side edges of the high grip member are locally worn or deformed, to thereby possibly reduce the endurance of the rotary member.
In this connection, in this fixing device, each side edge of the high grip member is not linear in the circumferential direction. Because of this configuration, the local wearing or deformation of the rotary member are lessened. This results increase of the endurance of the rotary member.
The 11th fixing belt has the advantageous effects (i) of the 4th fixing device, and further the following advantageous effects.
The uneven pattern on the surface of the high grip member is slanted with respect to the width direction. This feature produces a called edge effect (edge effect in the rotational direction (power transmission direction)) by the uneven pattern at the press contact portion of it with the rotary member. As a result, the gripping force by the high grip portion is increased, and an uneven pattern on a surface of a high grip member is slanted with respect to the width direction. The slip is prevented (at least its occurrence is extremely infrequent), and a stable fixing operation of the fixing device is secured.
If the uneven pattern on the surface of the high grip member is not slanted with respect to the width direction (it is parallel to the axial direction of the rotary member), a vibration by the drive power transmission (vibration due to the uneven pattern) may increase. However, in this fixing device, such a vibration is remarkably reduced since the uneven pattern on the surface of the high grip member is slanted with respect to the width direction. Accordingly, a smooth drive power transmission is secured.
In the 12th belt fixing device based on the 28th belt fixing device, the uneven patterns on the surface of the high grip member are axially symmetry with respect to the center line as view in the width direction of the fixing belt. Therefore, thrust forces (acting in the belt width direction) caused by the inclination of the uneven pattern are cancelled, so that the fixing belt stably runs.
The 13th fixing belt has the advantageous effects (i) of the 4th fixing device, and further the following advantageous effects.
The side edges of the fixing belt is brought into contact with the restricting members, so that such a behavior of the traveling fixing belt as to move aside is restricted.
Since the side edges of the fixing belt is brought into contact with the restricting members, the following advantageous effects are produced additionally.
The high grip members are fastened to both side ends of the fixing belt, so that the both side ends of the fixing belt are reinforced. Further, the high grip member comes into contact with the restricting member. Therefore, the endurance of the fixing belt is increased although such a construction is employed that the side end of the fixing belt comes into contact with the restricting member.
Therefore, the fixing belt may be thinned in structure. The fixing belt well follows an unevenness corresponding to the amounts of attached toner forming a toner image. This results in improvement of a fixing strength or a fixing uniformity. Further, a heat capacity of the fixing belt is small, so that it may be heated quickly.
In the 14th fixing belt based on the 13th fixing device, a rigidity of the high grip member in the belt width direction is larger than that in the belt circumferential direction. Therefore, the following advantageous effects are produced.
Since the rigidity of the high grip member in the belt circumferential direction is relatively small, when the high grip member is fastened to the side end of the fixing belt, the high grip member is expanded, so that the fitting of the high grip member to the belt side end is easy. Further, the high grip member is well fit around the side end of the fixing belt. Since the rigidity of the high grip member in the belt width direction is relatively large, its buckling strength is increased when it is brought into contact with the restricting members. As a result, such a behavior of the traveling fixing belt as to move aside is restricted satisfactorily.
The 15th belt fixing device has the advantageous effects comparable with those (i) of the 4th fixing device.
In this belt fixing device, a thermal expansion coefficient of each high grip member is substantially equal to that of the fixing belt. Therefore, the belt fixing device will additionally produce the following advantageous effects.
In this type of the fixing device, when it is operated, the fixing belt is heated to high temperature (e.g., approximately 150xc2x0 C. to 200xc2x0 C.). If the thermal expansion coefficient of the high grip portion fastened to each side end of the fixing belt is greatly different from than that of the fixing belt, a stress is generated at both the fastening faces by the thermal expansion coefficient difference between the fixing belt and the high grip members fastened to the side ends thereof. As a result, the bent side ends are easy to be broken or the high grip portion is easy to strip off the belt.
In this connection, in the 15th fixing device, the thermal expansion coefficient of the high grip member is substantially equal to that of the fixing belt (viz., it is made of a material having a thermal expansion coefficient substantially equal to that of the fixing belt). Therefore, little or a little stress that is caused in both the fastening faces by the thermal expansion coefficient difference between them is present. As a result, the problem of damaging the side ends of the fixing belt and the stripping of the high grip portion is solved. Consequently, the fixing device is improved in its endurance.
The 16th belt fixing device will produce the advantageous effects comparable with those (i) of the fourth fixing device.
Further, in the 16th belt fixing device, a high grip member is fastened to the fixing belt with a flexible adhesive layer being interposed therebetween.
In this type of the fixing device, during its operation, the fixing belt is heated to be at high temperature (150xc2x0 C. to 200xc2x0 C., for example). If the adhesive layer which fastens the high grip member to each side end of the fixing belt is not flexible, a thermal expansion coefficient difference between the fixing belt and the high grip member will give rise to the following problem: the belt end is easy to be broken or the high grip member is easy to peel off the fixing belt.
In this connection, in the 16th fixing device of this embodiment, the adhesive layer which fastens the high grip member to each side end of the fixing belt is flexible, the thermal expansion coefficient difference between the fixing belt and the high grip member is soaked up by the adhesive layer. Therefore, there is no chance that the ends of the fixing belt are broken or the high grip member peels off the belt. As a result, the fixing belt is improved in its endurance.
The 17th belt fixing device produces advantageous effects comparable with those (i) by the 4th belt fixing device.
This belt fixing device includes an oil coating mechanism for applying release oil to the surface of the fixing belt. Therefore, an offset phenomenon is unlikely to occur.
The high grip portion is capable of absorbing the oil, and hence produces the following advantageous effects.
Where the surface of the fixing belt is coated with the release oil, the oil will gradually move to the ends of the press contact portion between the fixing belt and the rotary member. However, in the 17th fixing device, the oil having reached the ends of the press contact portion is absorbed by the high grip member since the high grip members are fastened around both the side ends of the fixing belt in the fixing device and the high grip members have oil absorbing capability.
Therefore, the amount of oil present on the surfaces of both the side ends of the fixing belt, viz., the surfaces of the cloth of the high grip members, is small. As a result, a gripping force is satisfactorily secured at both the ends of the press contact portion. The slip is prevented (at least its occurrence is extremely infrequent), and a stable fixing operation of the fixing device is secured.
Thus, the 17th fixing device of this embodiment is able to stably fix the toner image although the surface of the fixing belt is coated with the release oil.
In the 18th belt fixing device based on the 17th belt fixing device, the high grip member allows the oil to flow in the belt circumferential direction. Therefore, if the high grip member is saturated with the oil, the oil entering the high grip member is moved in the belt circumferential direction and excluded out of the press contact portion by the pressing force.
Therefore, if the high grip member is saturated with oil applied thereto. The amount of oil present on the surfaces of both the side ends of the fixing belt, is small at the press contact portion. As a result, a gripping force is satisfactorily secured at both the ends of the press contact portion. The slip is prevented (at least its occurrence is extremely infrequent), and a stable fixing operation of the fixing device is secured.
The 19th belt fixing device produces the advantageous effects comparable with those (i) by the fourth fixing device.
In the belt fixing device, an offset phenomenon is unlikely to occur since an oil coating mechanism for applying release oil onto the surface of the endless belt.
Since the high grip portion is made of a composite material of high friction material and material having an oil absorbing capability, the following advantageous effects are produced.
Where the surface of the fixing belt is coated with the release oil, the oil will gradually move to the ends of the press contact portion. However, in the 19th fixing device, the oil having reached the ends of the press contact portion is absorbed by the material having an oil absorbing capability since the high grip portion is made of a composite material of high friction material and material having an oil absorbing capability.
Therefore, the amount of oil present on the surfaces of the high grip portions where the high friction material are exposed, is small. As a result, a gripping force is satisfactorily secured at both the ends of the press contact portion. The slip is prevented (at least its occurrence is extremely infrequent), and a stable fixing operation of the fixing device is secured.
Thus, the 19th belt fixing device is able to stably fix the toner image although the surface of the fixing belt is coated with the release oil.
Further, since the high grip member is made of a composite material of high friction material and material having an oil absorbing capability, its strength is also increased.
In the 20th belt fixing device based on any of the 8th to 18th fixing devices, the high grip portion is formed with an expandable endless belt having an inside diameter smaller than an outside diameter of each side end of the fixing belt when it is in a free state. Therefore, by the utilization of its expandability, the belt-like high grip member is expanded and fit to the side ends of the fixing belt to form a high grip portion well fit to and around the side ends of the fixing belt.
Where the high grip tape is wound around each side end of the fixing belt, there is a fear that high grip tape is easy to peel off the belt at its seam. In the 20th fixing belt, such a fear is not present and the belt-like high grip member doubles as a reinforcing member for the side end of the fixing belt. In this respect, a reliability of the fixing belt is improved. As a result, the fixing belt may be thinned in structure. The fixing belt well follows an unevenness corresponding to the amounts of attached toner forming a toner image. This results in improvement of a fixing strength or a fixing uniformity. Further, a heat capacity of the fixing belt is small, so that it may be heated quickly.
In the 21st belt fixing device based on any of the 8th to 18th fixing devices, the high grip tape is wound around each side end of the fixing belt and fastened thereto. Therefore, the high grip portion is formed by merely forming the exposing portions at both ends of the belt base itself. Accordingly, a reliability of the fixing device is improved. Further, the high grip portion of the belt fixing device may be manufactured more easily manufactured than a high grip portion formed by fitting high grip members like endless belts to the side ends of the fixing belt and fixing them thereto or by working the side ends of the belt into high grip portions.
In the 22nd belt fixing device based on the 21st fixing device, the winding start end 11 of the high grip tape is not lapped on the winding terminating end. Therefore, the following advantageous effects produced are comparable with those by the 5th belt fixing device.
In the 23rd belt fixing device based on the 21st fixing device, the winding start end of the high grip member is confronted with the winding terminating end in a state that a gap slanted to the axial direction of the rotary member is interposed therebetween. Therefore, the follow advantageous effects produced are comparable with those by the 21st belt fixing device.
In the 24th belt fixing device based on any of the ninth to 18th belt fixing device, since the high grip portion is formed with the cloth a surface of the high grip portion is defined by a number of vertical and horizontal fine ridges of the threads (woven or knitted) running crosswise and lengthwise. The fine ridge crossing pattern spreads substantially uniformly over the surface.
Accordingly, a vibration and a speed variation, which are generated at both ends of the fixing belt by a drive force transmission, are extremely reduced, thereby ensuring a smooth drive force transmission.
Since the fine ridge crossing pattern are formed by the threads, each ridge is rounded in cross section. With this configuration of the ridges, the stress concentration is lessened, and hence the endurance of the rotary member is increased.
Further, the high grip portion of this fixing device is superior to that formed with a rubber member of an uneven surface in the strength (particularly to shearing).
In the case of the high grip portion made of a film or a rubber member, for example, when a shearing force is applied to its edge, the edge first cracks, and then the crack rapidly propagates and the high grip portion is finally broken. In the case of the high grip portion made of the cloth, when the fiber at the edge of the cloth cracks to be broken, the breakage of the fiber does not propagates. That is, only one fiber at the edge is broken.
When the side edge of the belt is brought into contact with the inner surface of a flange (the guide ring) of the roller on which the fixing belt is put in order to restrict a zig-zag traveling of the fixing belt, a shearing force acting on the side edge of the belt is great in magnitude. In this fixing device, the high grip portions of cloth are provided on both side ends of the fixing belt. Therefore, the high grip portion is reluctant to its breakage and propagation of the breakage to the whole fixing belt 110 is also greatly impeded.
In the 25th belt fixing device based on any of the 4th to 9th, and 11th to 19th belt fixing devices, each side edge of the high grip member is not linear in the circumferential direction, and therefore the following advantageous effects are produced.
If each side edge of the high grip member is linear in the circumferential direction, positions of the rotary member, which is to be in pressing contact with the fixing belt, at which it is pressed against the side edges of the high grip member are locally worn or deformed, to thereby possibly reduce the endurance of the rotary member.
In this connection, in the 25th belt fixing device, each side edge of the high grip member is not linear in the circumferential direction. Because of this configuration, the local wearing or deformation of the rotary member are lessened. This results increase of the endurance of the rotary member.
In the 26th belt fixing device based on any of the 4th to 9th, and 11th to 19th belt fixing devices, the fixing belt is formed with an endless belt base, and a surface belt layer which is applied to the surface side of a central portion of the fixing base when viewed in the widthwise direction of the fixing base, and an outside diameter of the high grip portion is larger than that of the surface belt layer. Therefore, the high grip portions are pressed against both ends of the press contact portion between the fixing belt and the rotary member by great pressing forces. Therefore, a gripping force between the fixing belt and the rotary member is increased, the slip is prevented more reliably (at least its occurrence is extremely less frequent). And a stable fixing operation of the fixing device is secured.
In the 27th belt fixing device based on any of the 9th to 19th belt fixing devices, each end of a high grip member as viewed in the width direction is beveled. Therefore, the stress concentration on the rotary member by the ends of the high grip member is lessened, and hence the endurance of the rotary member is further increased.
Accordingly, with the beveled end faces, the stress concentration on the rotary member by the ends of the high grip member is lessened, and hence the endurance of the rotary member is increased, although this embodiment has such a construction that the outside diameter of the high grip member is larger than that of the surface belt layer, and therefore, at the ends of the press contact portion between the fixing belt and the rotary member, the high grip members are pressed against the rotary member by a larger pressing force.
In the 28th belt fixing device based on the 27th belt fixing device, each beveled surface is smoothed.
Accordingly, the endurance of the pressure application roller 120 is further increased.
In the 29th belt fixing device based on any of the 9th to 14th, 17th and 18th belt fixing devices, a thermal expansion coefficient of each high grip member is substantially equal to that of the fixing belt. Therefore, the belt fixing device will additionally produce the following advantageous effects.
As already described, in this type of the fixing device, when it is operated, the fixing belt is heated to high temperature (e.g., approximately 150xc2x0 C. to 200xc2x0 C.). If the thermal expansion coefficient of the high grip portion fastened to each side end of the fixing belt is greatly different from than that of the fixing belt, and if the adhesive layer is not flexible, a stress will be generated at both the fastening faces by the thermal expansion coefficient difference between the fixing belt and the high grip members fastened to the side ends thereof. As a result, the side ends are easy to be broken or the high grip portion is easy to strip off the belt.
In this connection, in the 29th belt fixing device, the thermal expansion coefficient of the high grip member is substantially equal to that of the fixing belt (viz., it is made of a material having a thermal expansion coefficient substantially equal to that of the fixing belt). Therefore, little or a little stress that is caused in both the fastening faces by the thermal expansion coefficient difference between them is present. As a result, the problem of damaging the side ends of the fixing belt and the stripping of the high grip portion is solved. Consequently, the endurance of the fixing device is increased.
In the 30th belt fixing device based on any of the 9th to 14th, 17th and 18th belt fixing devices, a high grip member is fastened to the fixing belt with a flexible adhesive layer being interposed therebetween. Therefore, the 30th belt fixing device will produces the advantageous effects comparable with those by the 16th belt fixing device.
In the 31st belt fixing device based on any of the 9th to 14th, 17th and 18th belt fixing devices, an oil coating mechanism for applying release oil to the surface of the fixing belt is provided. Therefore, an offset phenomenon is unlikely to occur.
As described above, where the surface of the fixing belt is coated with the release oil, the oil will gradually move to the ends of the press contact portion between the fixing belt and the rotary member. However, in the 31st fixing device, the oil having reached the ends of the press contact portion is absorbed by the high grip member since the high grip members are fastened around both the side ends of the fixing belt in the fixing device and the high grip members have oil absorbing capability.
Therefore, the amount of oil present on the surfaces of both the side ends of the fixing belt, viz., the surfaces of the cloth of the high grip members, is small. As a result, a gripping force is satisfactorily secured at both the ends of the press contact portion. The slip is prevented (at least its occurrence is extremely infrequent), and a stable fixing operation of the fixing device is secured.
Thus, the 31st fixing device of this embodiment is able to stably fix the toner image although the surface of the fixing belt is coated with the release oil.
In the 32nd belt fixing device based on the 31st belt fixing device, the high grip member allows the oil to flow in the belt circumferential direction. Therefore, if the high grip member is saturated with the oil, the oil entering the high grip member is moved in the belt circumferential direction and excluded out of the press contact portion by the pressing force.
Therefore, if the high grip member is saturated with oil applied thereto. The amount of oil present on the surfaces of both the side ends of the fixing belt, is small at the press contact portion. As a result, a gripping force is satisfactorily secured at both the ends of the press contact portion. The slip is prevented (at least its occurrence is extremely infrequent), and a stable fixing operation of the fixing device is secured.
In the 33rd belt fixing device based on the 31st belt fixing device, the release oil, which is applied by the oil coating mechanism, is applied to within only the contact portion of the fixing belt where it is brought into contact with the recording medium. Therefore, the applied oil is almost all absorbed by or transferred to the recording medium when the recording medium passes therethrough.
Accordingly, there is little chance that the release oil flows to the non-contact portions not in contact with the recording medium, i.e., the high grip portion. As a result, a more stable fixing operation of the fixing device is performed.
In the 34th belt fixing device based on the 4th to 16th belt fixing devices, an oil coating mechanism for applying release oil to the surface of the fixing belt is provided. Therefore, an offset phenomenon is unlikely to occur.
The high grip member is provided at both the side ends of the fixing belt, and is permeable to the oil, and is fastened to both the side ends of the fixing belt with an adhesive layer having an absorbing capability being interposed therebetween. Accordingly, the oil having entered the ends of the press contact portion is absorbed by the adhesive layer through the high grip members.
Therefore, the amount of oil present on the surfaces of both the side ends of the fixing belt, is small. As a result, a gripping force is satisfactorily secured at both the ends of the press contact portion. The slip is prevented (at least its occurrence is extremely infrequent), and a stable fixing operation of the fixing device is secured.
Thus, the 34th fixing device of this embodiment is able to stably fix the toner image although the surface of the fixing belt is coated with the release oil.
In the 35th belt fixing device based on the 34th belt fixing device, the release oil, which is applied by the oil coating mechanism, is applied to within only the contact portion of the fixing belt where it is brought into contact with the recording medium. Therefore, the applied oil is almost all absorbed by or transferred to the recording medium when the recording medium passes therethrough.
Accordingly, there is little chance that the release oil flows to the non-contact portions not in contact with the recording medium, i.e., the high grip portion. As a result, a more stable fixing operation of the fixing device is performed.
In the 18th image forming apparatus based on any of the 7th to 10th, and 13th to 15th image forming apparatuses, the release oil, which is applied by the oil coating mechanism, is applied to within only the contact portion of the fixing belt where it is brought into contact with the recording medium. Therefore, the applied oil is almost all absorbed by or transferred to the recording medium when the recording medium passes therethrough.
Accordingly, there is little chance that the release oil flows to the non-contact portions not in contact with the recording medium, i.e., (1) the contact portion between the rotary member and the backup roller in the non-contact portion not in contact with the fixing belt and (2) the nip between the endless belt and the backup roller. As a result, a more stable fixing operation of the fixing device is performed.
In the 36th belt fixing device based on any of the 17th to 29th belt fixing devices, the release oil, which is applied by the oil coating mechanism, is applied to within only the contact portion of the fixing belt where it is brought into contact with the recording medium. Therefore, the applied oil is almost all absorbed by or transferred to the recording medium when the recording medium passes therethrough.
Accordingly, there is little chance that the release oil flows to the non-contact portions not in contact with the recording medium, i.e., the high grip portion. As a result, a more stable fixing operation of the fixing device is performed.
The 37th belt fixing device, which is based on any of the first to 19th belt fixing devices, is capable of fixing toner images on both sides of the recording medium. Therefore, there is a case that a recording medium having toner images formed on both sides thereof passes through the press contact portion in the fixing device.
Sometimes the toner on the recording medium reduces the friction coefficient between the recording medium and the rotary member. And it interrupts the oil absorbing by the recording medium. Therefore, in a case where the toner images are formed on both sides of the recording medium, the recording medium is more likely to slip when comparing with a case where the toner image is formed on one side of the recording medium.
In this connection, in the 37th belt fixing device, the high grip portions are provided at both side ends of the fixing belt. Therefore, even when toner images are formed on both sides of the recording medium, the slip does not occur (at least its occurrence is extremely infrequent). As a result, a stable fixing operation of the fixing device is secured.
Thus, the 37the belt fixing device is capable of fixing toner images suffering from no (at least little) image disarrangement on both sides of the recording medium.
The 38th belt fixing device, which is based on any of the first to 19th belt fixing devices, is capable of fixing a full color image by superimposing a plurality of different colors. Therefore, there is a case that a recording medium having a full color image formed on at least one side thereof passes through the press contact portion in the fixing device.
As described above, sometimes the toner on the recording medium reduces the friction coefficient between the recording medium and the rotary member, and it interrupts the oil absorbing by the recording medium. Therefore, in a case where the full color image by superimposing a plurality of different colors is formed on the recording medium, the recording medium is more likely to slip when comparing with a case where the toner image of monochromatic color is formed on the recording medium.
In this connection, in the 38th belt fixing device, the high grip portions are provided at both side ends of the fixing belt. Therefore, even when the full color image by superimposing a plurality of different colors is formed on the recording medium, the slip does not occur (at least its occurrence is extremely infrequent). As a result, a stable fixing operation of the fixing device is secured.
Thus, the 38the belt fixing device is capable of fixing a full color image suffering from no (at least little) image disarrangement. When combined with the 37th belt fixing device, it is capable of fixing full color toner images no (at least little) suffering from image disarrangement on both sides of the recording medium.
The present invention further provides the following fixing devices:
(1) A fixing device comprising:
a first rotary member;
a second rotary member contacting the first rotary member and forming a nip in corporation with the first rotary member;
the first and second rotary members having mutually contacting surfaces that are maintained in contact with each other regardless of whether or not a sheet is passed through the nip;
at least one of first and second rotary members having a first surface and a second surface that is higher in at least one of frictional characteristic, oil absorbing characteristic, oil permeable characteristic and oil-flow permitting characteristic than the first surface and that forms at least a part of a corresponding one of the mutually contacting surfaces.
(2) A fixing device according to (1), wherein the first rotary member has the first and second surfaces.
(3) A fixing device according to claim (1), wherein the second rotary member has the first and second surfaces.
(4) A fixing device according to (1), wherein each of the second rotary member has the first and second surfaces.
(5) A fixing device comprising:
a laterally elongating rotary member;
an endless belt contacting the first rotary member and forming a nip in corporation with the first rotary member;
a backup member keeping the endless belt in contact with the first rotary member;
at least one of the first rotary member, the endless belt and the backup member having a first surface and a second surface that is higher in at least one of frictional characteristic, oil absorbing characteristic, oil permeable characteristic and oil-flow permitting characteristic than the first surface;
the first surface being laterally corresponding in location to a region of the nip wherein the region is contactable with a sheet passed through the nip;
the second surface being situated laterally outside the region, and maintained in contact with another one of the rotary member, the endless belt and the backup member.
(6) A fixing device of (5), wherein the rotary member has the first and second surfaces.
(7) A fixing device of (5), wherein the endless belt has the first and second surfaces.
(8) A fixing device of (5), wherein the backup member has the first and second surfaces.
(9) A fixing device of (5), wherein each of the rotary member and the endless belt has the first and second surfaces.
(10) A fixing device of (5), wherein each of the rotary member and the backup member has the first and second surfaces.
(11) A fixing device of (5), wherein each of the endless belt and the backup member has the first and second surfaces.
(12) A fixing device of (5), wherein each of the rotary member and the backup member has the first and second surfaces, and the endless belt has the first surface on each of opposite surfaces of the endless belt, and the second surface on each of the opposite surfaces of the endless belt.
(13) A fixing device of any one of (1) to (12), wherein the second surface is defined by a perforated surface having a large number of holes.
(14) A fixing device of any one of (1) to (12), wherein the second surface is defined by a mesh material.
(15) A fixing device of any one of (1) to (12), wherein the second surface is defined by a rubber having a large number of laterally elongating ribs.
(16) A fixing device of any one of (1) to (12), wherein the second surface is defined by a heat-resistant tape having a large number of laterally elongating ribs.
(17) A fixing device of any one of (1) to (12), wherein the second surface is defined by a silicone rubber sponge.
(18) A fixing device of any one of (1) to (12), wherein the second surface is defined by a combination of a large number of particles and adhesive.
(19) A fixing device of any one of (1) to (12), wherein the second surface is defined by a high friction material having protruded and recessed portions.
(20) A fixing device of any one of (1) to (12), wherein the second surface is defined by an expandable endless belt, and an inner circumferential length of the expandable endless belt is normally smaller than an outer circumferential length of the first surface before the expandable belt is installed in place to define the second surface.
(21) A fixing device of any one of (1) to (12), wherein the second surface is defined by a cloth.
(22) A fixing device of any one of (1) to (12), wherein the second surface is protruded relative to the first surface.
(23) A fixing device of any one of (1) to (12), wherein the second surface is defined by an open-cell porous material.
(24) A fixing device of any one of (1) to (12), wherein the second surface is defined by a synthetic-resin-made, heat-resistant sheet having a large number of cavities.
(25) A fixing device of any one of (1) to (12), wherein the second surface is defined by a synthetic-resin-made, heat-resistant sheet having a large number of through-holes.
(26) A fixing device of any one of (1) to (12), wherein the second surface has a beveled surface as a lateral boundary.
(27) A fixing device of any one of (1) to (12), wherein the second surface has a laterally offsetting edge.
(28) A fixing device of any one of (1) to (12), wherein the second surface has a varying, lateral length.
(29) A fixing device of any one of (1) to (12), wherein the second surface is defined by repeating patterns each slanted with respect to a lateral direction.
(30) A fixing device of any one of (1) to (12), wherein the second surface is defined by a member supported on a base, and the high grip member is laterally protruded beyond a lateral end of the base.
(31) A fixing device of any one of (1) to (12), wherein the second surface is defined by a member having a larger rigidity in a lateral direction than in a circumferential direction.
(32) A fixing device of any one of (1) to (12), wherein the second surface is defined by a member supported on a base, and the member is substantially equal in a thermal expansion coefficient to the base.
(33) A fixing device of any one of (1) to (12), wherein the second surface is defined by a combination of a high friction material and an oil absorbing material.
(34) A fixing device of any one of (1) to (4), further comprising:
an annular groove provided on at least one of the first and second rotary members, the annular groove being laterally situated between a region of the nip and the mutually contacting surfaces wherein the region is contactable with a sheet passed through the nip.
(35) A fixing device of any one of (5) to (12), further comprising:
an annular groove provided on at least one of the rotary member and the backup member, the annular groove being laterally situated between the region of the nip and mutually contacting surfaces of the rotary member and the backup member, wherein the mutually contacting surfaces are maintained in contact with each other regardless of whether or not a sheet is passed through the nip.
(36) A fixing device comprising:
a first rotary member;
a second rotary member contacting the first rotary member and forming a nip in corporation with the first rotary member;
the first and second rotary members having mutually contacting surfaces that are maintained in contact with each other regardless of whether or not a sheet is passed through the nip;
an annular groove provided on at least one of the first and second rotary members, the annular groove being laterally situated between a region of the nip and the mutually contacting surfaces wherein the region is contactable with a sheet passed through the nip.
(37) A fixing device comprising:
a laterally elongating rotary member;
an endless belt contacting the first rotary member and forming a nip in corporation with the first rotary member;
a backup member keeping the endless belt in contact with the first rotary member;
an annular groove provided on at least one of the rotary member and the backup member, the annular groove being laterally situated between a region of the nip and mutually contacting surfaces of the rotary member and the backup member, wherein the region is contactable with a sheet passed through the nip, and wherein the mutually contacting surfaces are maintained in contact with each other regardless of whether or not a sheet is passed through the nip.
The present disclosure relates to the subject matter contained in Japanese patent application Nos.:
1) Hei. 11-56215 (filed on Mar. 3, 1999);
2) Hei. 11-56216 (filed on Mar. 3, 1999);
3) Hei. 11-185083 (filed on Jun. 30, 1999);
4) Hei. 11-194761 (filed on Jul. 8, 1999);
5) Hei. 11-194762 (filed on Jul. 8, 1999);
6) Hei. 11-194763 (filed on Jul. 8, 1999);
7) Hei. 11-247031 (filed on Sep. 1, 1999);
8) Hei. 11-247030 (filed on Sep. 1, 1999);
9) Hei. 11-247034 (filed on Sep. 1, 1999);
10) Hei. 11-247033 (filed on Sep. 1, 1999);
11) Hei. 11-247037 (filed on Sep. 1, 1999); and
12) Hei. 11-247036 (filed on Sep. 1, 1999), all of which are expressly incorporated herein by reference in their entireties.